I thought the 5 and leave one was because many old revolvers were not drop safe and the hammer, which has the firing pin built in, could strike the primer should said revolver land on hammer, and there would be a discharge of the weapon.
Load one, skip one, load 4 more is what we use for our revolvers in the cowboy shoots. This centers the empty chamber directly below the hammer so those using a Colt or Uberti do not have to worry about hitting the hammer and setting one off in the holster. I carry a Ruger Vaquero so it’s not an issue for me to load 6 but the COF calls for 5 shots.